Vagrant harlequin ducks feed on a buffet of blennies

Typically found in eastern Russia, northern North America, Greenland, and Iceland, harlequin ducks (Histrionicus histrionicus) breed near whitewater rivers and spend the winter on rocky coastlines, where they feed on invertebrates and small fishes (Ecology 1986; doi.org/10.2307/1939078). Despite their temperate and subarctic distribution, two vagrant female harlequin ducks were observed in the Corpus Christi Ship Channel near the Port Aransas Jetty (Port Aransas, TX) in February 2022, representing only the third known confirmation of the species in Texas. The ducks remained in the channel for several days and were observed feeding on Molly Miller blennies (Scartella cristata), a common cryptobenthic fish with a wide distribution along tropical and subtropical coastlines. The dredged shipping channel connects the Gulf of Mexico to a ~380-km-long estuarine system and directly flows into the Mission-Aransas Estuary, a highly productive marine environment important for commercial fishing and wintering diving waterbirds. During the winter, harlequin ducks forage along rocky intertidal zones with wave exposure (Estuar Coast Shelf S 2019; doi.org/10.1016/j.ecss.2019.04.024). Thus, the rock piles and strong tides in the shipping channel may have provided the ducks’ only suitable feeding habitat in a system dominated by soft sediments and limited water movement. With their exceptional diving abilities in harsh environments, the sea ducks had access to an ample buffet of blennies, which were evidently unprepared for this skilled predator. Although these hardy ducks exhibit high site fidelity and are of low conservation concern globally, they face habitat loss and population declines in eastern North America. Vagrants are often accidentals, but the harlequin ducks’ journey may have been intentional (Biol Conserv 2018; doi.org/10.1016/j.biocon.2018.06.006); disturbances to their wintering habitat in Maine or eastern Canada could drive bold individuals to search for alternative feeding grounds. Will habitat loss incur novel trophic interactions, particularly involving migratory birds?